This invention relates generally to collapsible pallet racks and more particularly to a collapsible and stackable pallet for shipping and storing breakable material.
Partially collapsible or foldable steel pallets are known for use in place of wood pallets in shipping heavy and awkward articles such as automobile windshields. Steel pallets are very durable, allowing for prolonged use. Moreover, partially collapsible pallets allow for reduced shipping volume, decreasing the cost of relocating empty pallets for reuse. Accordingly, it is known generally to use partially collapsible steel pallets to ship breakable goods, such as automobile windshields.
The shipment of breakable goods present unique challenges in the design of reusable pallets. For example, if a pane of glass is not properly secured within the pallet, unacceptable levels of breakage occur in shipment. Accordingly, it is known to use dunnage when shipping windshields. “Dunnage” is simply packing material which is added to the pallet so as to make the shipped material more secure. Of course, the addition of dunnage to the pallet takes time, and increases the potential for breakage when improperly performed. Moreover, the need for dunnage increases the cost of shipping. All of these problems are exacerbated when a partial pallet (a pallet that is not completely filled) is to be shipped.
It is also known to design a pallet so as to provide support at a plurality of locations when shipping a pane of glass. U.S. Pat. No. 5,154,310 to Massey is an example of this type of pallet. In accordance with the '310 patent, an end nestable stackable container is provided with a means to firmly contain material being shipped. Four point of contact are provided for the material to be shipped. The '310 patent accomplishes this by providing hold down arms which can be pivoted over the top of the material being shipped, so as to provide contact along the top edge of the material. Contact on two sides of the material being shipped is provided by a side stabilizing mechanism. The fourth point of contact is along the bottom of the material. The device disclosed in the '310 patent is useful when shipping empty pallets. However, because the pallet is only partially collapsible, allowing the empty pallets to be nested, the number of pallets which can be safely stacked before the stack starts to lean is limited.
The device disclosed in the '310 patent is also useful when shipping a number of panes which are of a uniform shape and size. However, in certain applications it would be advantageous to ship glass of differing shapes and sizes within a single pallet. For example, the secondary windshield market provides replacement windshields for all makes and models of vehicles. It is impractical for retail stores to maintain a supply of every shape and size windshield for every make and model of vehicle. Thus, the secondary windshield market has evolved into a make to order market. In a make to order market, when a windshield of a particular size is needed, an order is placed to a manufacturing facility. The facility then manufactures a replacement windshield. The replacement windshield is next packaged, along with other windshields, and transported to a distribution center, for eventual shipment to the location which placed the initial order.
Obviously, a number of alternative distribution models exist. For example, certain sized windshields may be so commonly required as replacements that a certain level of inventory is desired at the distribution center. Alternatively, more or fewer distribution points may be included in a particular distribution model. Regardless of the model, however, it is advantageous to be able to place windshields of various sizes and shapes on a single pallet. The presence of windshields of non-uniform shape or size on a single pallet is called a “mixed pallet.” Use of a mixed pallet allows for optimization of the use of pallet volume when shipping windshields, so that fewer pallets are required. As the number of pallets is reduced for a given number of windshields, the overall required shipping volume and weight is reduced. When using steel pallets, the reduced weight can be significant. Of course, the reduced number of pallets also results in cost savings when returning the pallets to the manufacturing facility for reuse.
The shipment of full pallets, mixed pallets or partial pallets of windshields present a number of additional challenges. This is due, in part, because windshields are not of a uniform shape or size. Typical variation in windshield shape and size is discussed with reference to FIGS. 12-14. FIG. 12 is a perspective view of a windshield. As shown in FIG. 12, windshield 1200 is curved from corner 1202 to corner 1204. Windshield 1200 is also curved between upper midpoint 1206 and lower midpoint 1208. This is shown more clearly in FIG. 14 which is discussed below.
Referring now to FIG. 13, a front view of windshield 1200 is shown. Also shown in FIG. 13 is a front view of windshield 1210, which is located behind windshield 1200. As is clear from FIG. 13, windshield 1200 is both longer and taller than windshield 1210.
FIG. 14 is a side view of windshield 1200 and windshield 1210 in a substantially upright position. Front face 1212 (outside when installed in a vehicle) of windshield 1200 and front face 1214 of windshield 1210 are curved. Additionally, windshield 1200 and windshield 1210 are curved from end to end. This is shown in FIG. 15, which is a top plan view of windshield 1200 and windshield 1210.
Thus, ear 1216 and ear 1218 of windshield 1210 are located behind the midpoint of the rear face of windshield 1210, which is shown in FIG. 14 as dashed line 1230. Similarly, ear 1218 and ear 1220 of windshield 1200 are located behind the midpoint of the rear face of windshield 1200, which is shown in FIG. 14 as dashed line 1232. As is apparent from FIG. 14, ear 1220 of windshield 1200 extends farther back from dashed line 1232 than ear 1216 of windshield 1210 extends back from dashed line 1230.
Since it is desirable to maintain all of the windshield within the protective box or envelope defined by the outer boundaries of the pallet to minimize breakage, and since windshields are typically shipped in a generally upright position, a pallet used to ship windshields of multiple heights must be high enough to enclose the tallest windshield to be shipped. Obviously, when shipping shorter windshields, this results in a pallet of unnecessary weight and volume, increasing shipping costs.
Moreover, in order to ensure the ears of the windshield (the outermost ends) are maintained within the envelope of the pallet, it is known to use a stop. A “stop”, as used herein, is an object that protrudes into the pallet envelope to maintain spacing between the windshield and the end of the pallet. The stop protrudes into the pallet and contacts the rear face of the windshield. Because windshields are of varying curvature and length, the distance the stop must protrude into the envelope of the pallet varies. Obviously, sizing the stops to ensure the windshields of greatest curvature and length are maintained within the envelope of the pallet results in wasted space when windshields of lesser curvature and length are shipped. This decrease in shipping density of the pallet, can result in more pallets being required to ship a given number of windshields. While some present art systems allow for adjustable stops, these systems include a number of moving parts, and take a significant amount of time to adjust.
Another problem caused by the curvature of windshields is that the center of gravity of the pallet will not be the volumetric center of the pallet. Therefore, when the windshields are secured within a pallet, a torque is created. This is typically not a problem when a single pallet is considered, or when the pallet is not collapsible. However, when stacking collapsible pallets wherein an upright post is inserted into a holder, the torque will tend to unseat the post from the holder. Thus, stacked pallets can develop a lean.
An additional problem is presented because of the varying lengths of present day windshields. Typically, a restraint is incorporated on each side of a pallet to maintain loaded windshields within the envelope of the pallet. A “restraint”, as used herein, is an object that maintains a windshield within the envelope of the pallet at the sides of the pallet. Positioning the restraints to allow for the shipment of the longest windshield expected to be shipped, results in an undesirably large lateral area within which a windshield is allowed to move before being laterally constrained. Although it is known to provide adjustable lateral restraints, these restraints include a number of parts which can be misplaced and/or are time consuming to adjust.
It is desirable, therefore, to provide a device which allows for shipment of vehicle replacement glass of non-uniform shape and/or size while minimizing breakage of the glass in shipping. It is further desired that the device minimize the required amount of dunnage, and be simple to use. Moreover, it is desired that the device be of simple, lightweight and inexpensive construction. It is desired that the pallet be stackable even when empty and collapsed. It is also desired to have a shipping pallet that is versatile enough to ship tall windshields without wasting weight and volume when shipping short windshields. It is further desirable to provide stops which use a minimum number of parts and which can be quickly and easily changed to the proper distance of protrusion into the pallet. Moreover, it is desired to have a collapsible pallet that will not lean when stacked. Additionally, it is desired to provide a restraint which is quickly and easily repositioned to a lateral position dictated by the longest windshield in the pallet being shipped.